The present invention relates to a method of manufacturing a spin valve magnetoresistive effect (SVMR) element utilizing a giant magnetoresistive effect (GMR) and to a method of manufacturing a thin-film magnetic head with the SVMR element, used in for example a hard disk device (HDD).
Recently, thin-film magnetic heads with SVMR elements that provide one of GMR characteristics are actually mass-produced in order to satisfy the requirement for ever increasing data storage densities in today""s magnetic storage systems like HDD units. The SVMR thin-film structure includes first and second thin-film layers of a ferromagnetic material separated by a thin-film layer of non-magnetic metallic material, and an adjacent layer of anti-ferromagnetic material is formed in physical contact with the second ferromagnetic layer to provide exchange bias magnetic field by exchange coupling at the interface of the layers. The magnetization direction in the second ferromagnetic layer is constrained or maintained by the exchange coupling, hereinafter the second ferromagnetic layer is called xe2x80x9cpinned layerxe2x80x9d. On the other hand, the magnetization direction of the first ferromagnetic layer is free to rotate in response to an externally applied magnetic field, hereinafter the first ferromagnetic layer is called xe2x80x9cfree layerxe2x80x9d. The direction of the magnetization in the free layer changes between parallel and anti-parallel against the direction of the magnetization in the pinned layer, and hence the magneto-resistance greatly changes and GMR characteristics are obtained.
Japanese unexamined patent publication No. 11-97763 discloses that a magnetostriction constant xcex of a free layer in the SVMR element should be desired to be within a range of xe2x88x921.0xc3x9710xe2x88x926 to +1.0xc3x9710xe2x88x926. This is because the asymmetry of output signal shape of the SVMR element will collapse if the magnetostriction constant xcex of the free layer becomes larger toward the positive side, and a magnetic wall may be produced in the free layer causing Bulkhauzen noises to increase if the absolute value of the magnetostriction constant xcex becomes large. Furthermore, if the magnetostriction constant xcex becomes larger toward the negative side, the coercive force Hk of the free layer increases causing the output of the SVMR element to reduce.
In order to keep the magnetostriction constant xcex of the free layer within the range of xe2x88x921.0xc3x9710xe2x88x926 to +1.0xc3x9710xe2x88x926, Japanese unexamined patent publication No. 11-97763 proposes to make the free layer from a NiFe single layer with Ni-composition of 81.5 to 83.0 wt %.
Japanese unexamined patent publication No.11-96516 concerns a technique for controlling the magnetization direction of a pinned layer of a SVMR element and discloses to form a free layer in a two-layers structure of a NiFe layer and a CoFeB layer.
However, according to the known techniques disclosed in the above-mentioned Japanese unexamined patent publication Nos. 11-97763 and 11-96516, the magnetostriction constant of the free layer will vary depending upon the thickness change in the NiFe layer of the free layer. Namely, if the NiFe layer becomes thin, the magnetostriction will become large toward the positive direction and thus it is difficult to properly control the magnetostriction causing the production stability of SVMR element to spoil greatly.
It is therefore an object of the present invention to provide a manufacturing method of a SVMR element and a manufacturing method of a thin-film magnetic head with the SVMR element, whereby control of magnetostriction can be easily performed.
Another object of the present invention is to provide a manufacturing method of a SVMR element and a manufacturing method of a thin-film magnetic head with the SVMR element, whereby excellent production stability can be expected.
According to the present invention, a method of manufacturing a SVMR element and a manufacturing method of a thin-film magnetic head with the SVMR element are provided. The SVMR element has a non-magnetic metallic thin-film layer, first and second ferromagnetic thin-film layers (free and pinned layers) formed to sandwich the non-magnetic metallic thin-film layer and an anti-ferromagnetic thin-film layer formed in contact with a surface of the second ferromagnetic thin-film layer. This surface is opposite to the non-magnetic metallic thin-film layer. The first ferromagnetic thin-film layer has a two-layers structure of a NiFe layer and a CoFe layer. Particularly, according to the present invention, the method includes a step of depositing the first ferromagnetic thin-film layer, the non-magnetic metallic thin-film layer, the second ferromagnetic thin-film layer and the anti-ferromagnetic thin-film layer, and a step of annealing, thereafter, the deposited layers so that change in magnetostriction depending upon variation of a thickness of the NiFe layer becomes small.
According to the present invention, also, a method of manufacturing a SVMR element includes a step of depositing a first ferromagnetic thin-film layer (free layer) to form a two-layers structure of a NiFe layer and a CoFe layer, a step of depositing a non-magnetic metallic thin-film layer on the first ferromagnetic thin-film layer, a step of depositing a second ferromagnetic thin-film layer (pinned layer) on the non-magnetic metallic thin-film layer, a step of depositing an anti-ferromagnetic thin-film layer on the second ferromagnetic thin-film layer, and a step of annealing, thereafter, the deposited layers so that change in magnetostriction depending upon variation of a thickness of the NiFe layer becomes small.
According to the present invention, furthermore, a method of manufacturing a SVMR element includes a step of depositing an anti-ferromagnetic thin-film layer, a step of depositing a second ferromagnetic thin-film layer (pinned layer) on the anti-ferromagnetic thin-film layer, a step of depositing a non-magnetic metallic thin-film layer on the second ferromagnetic thin-film layer, a step of depositing a first ferromagnetic thin-film layer (free layer) on the non-magnetic metallic thin-film layer to form a two-layers structure of a CoFe layer and a NiFe layer, and a step of annealing, thereafter, the deposited layers so that change in magnetostriction depending upon variation of a thickness of the NiFe layer becomes small.
The free layer has a two-layers structure of a CoFe layer and a NiFe layer, and annealing is performed so that change in magnetostriction depending upon variation of a thickness of the NiFe layer becomes small. Thus, the magnetostriction constant of the free layer can be easily controlled within a desired range, for example within a range of xe2x88x921.0xc3x9710xe2x88x926 to +1.0xc3x9710xe2x88x926, and therefore excellent production stability can be expected.
It is preferred that the CoFe layer has a thickness within a range of 1.2 to 4.3 nm.
It is also preferred that the NiFe layer has a thickness of 2 nm or more.
It is preferred that the NiFe layer has a composition of Ni within a range of 81 to 83 at %.
It is preferred that the CoFe layer has a composition of Fe within a range of 5 to 17 at %.
It is further preferred that the NiFe layer has a composition of Ni within a range of 81 to 83 at %, and the CoFe layer has a thickness within a range of 1.2 to 4.3 nm.
It is preferred that the annealing step includes annealing the deposited layers at a temperature of 200xc2x0 C. or more.
Further objects and advantages of the present invention will be apparent from the following description of the preferred embodiments of the invention as illustrated in the accompanying drawings.